Raman Effect of Some Complex Phosphates

The most common acid of pentavalent phosphorus is orthophosphoric acid, H3PO4, and all the other acids may be looked upon as being derived from it by the process of dehydration. Thus two molecules of the ortho acid between them can lose one molecule of water forming pyrophosphoric acid, H4P2O7. Upon still stronger dehydration one molecule of water can be eliminated from each molecule of the ortho acid and the resulting product HPO3 is known as metaphosphoric acid which was extensively investigated by Graham (1). Metaphosphoric acid and its salts show a great tendency to polymerize to (NaPo3)n and will form crystalline or glass-like materials, the polymetaphosphates. They show a similarity to the corresponding silicon can have only a positive charge of four units. The polymetaions are enclosed within oxygen-ion tetrahedra and that some of the divalent oxygen ions are common to two tetrahedra. These ideas have been developed by Bragg (2) and Pauling (3) in the case of silicates